Generally, cancer results from the deregulation of the normal processes that control cell division, differentiation and apoptotic cell death. Apoptosis (programmed cell death) plays essential roles in embryonic development and pathogenesis of various diseases, such as degenerative neuronal diseases, cardiovascular diseases and cancer. One of the most commonly studied pathways, which involves kinase regulation of apoptosis, is cellular signaling from growth factor receptors at the cell surface to the nucleus (Crews and Erikson, Cell, 74:215-17, 1993).
Protein tyrosine kinases (PTKs) catalyze the phosphorylation of specific tyrosyl residues in various proteins involved in the regulation of cell growth and differentiation. (A. F. Wilks, Progress in Growth Factor Research, 1990, 2, 97-111; S. A. Courtneidge, Dev. Supp. I, 1993, 57-64; J. A. Cooper, Semin. Cell Biol., 1994, 5(6), 377-387; R. F. Paulson, Semin. Immunol., 1995, 7(4), 267-277; A. C. Chan, Curr. Opin. Immunol., 1996, 8(3), 394-401). Inappropriate or uncontrolled activation of many PTKs, i.e. aberrant PTK activity, for example by over-expression or mutation, has been shown to result in uncontrolled cell growth.
Aberrant protein tyrosine kinase (PTK) activity has been implicated in a variety of disorders including psoriasis, rheumatoid arthritis, bronchitis, as well as cancer. Development of effective treatments for such disorders is a constant and ongoing enterprise in the medical field. The ErbB family of PTKs, which includes ErbB-2, EGFR, ErbB-3 and ErbB-4, is one group of PTKs that has attracted interest as a therapeutic target. Currently, of special interest, is the role of ErbB family PTKs in hyperproliferative disorders, particularly human malignancies. Elevated EGFR activity has, for example, been implicated in non-small cell lung, bladder, and head and neck cancers. Furthermore, increased ErbB-2 activity has been implicated in breast, ovarian, gastric and pancreatic cancers. Overexpression of HRG and/or HER3 has been reported in numerous cancers, including gastric, ovarian, prostate, bladder, and breast tumors and is associated with poor prognosis (B. Tanner, J Clin Oncol. 2006, 24(26):4317-23; M. Hayashi, Clin. Cancer Res. 2008.14(23):7843-9.; H. Kaya, Eur J Gynaecol Oncol. 2008; 29(4):350-6). Consequently, inhibition of ErbB family PTKs should provide a treatment for disorders characterized by aberrant ErbB family PTK activity. The biological role of ErbB family PTKs and their implication in various disease states is discussed, for instance in U.S. Pat. No. 5,773,476; International Patent Application WO 99/35146; M. C. Hung et al, Seminars in Oncology, 26: 4, Suppl. 12 (August) 1999, 51-59; Ullrich et al, Cell, 61: 203-212, Apr. 20, 1990; Modjtahedi et al, Intl J. of Oncology, 13: 335-342, 1998; and J. R. Woodburn, Pharmacol. Ther., 82: 2-3, 241-250, 1999, it is generally accepted that inhibitors of ErbB family kinases will be useful for the treatment of such cancers or other condition associated with ErbB family kinases.
Mitogen-activated protein (MAP) Kinase/extracellular signal-regulated kinase (ERK) kinase (hereinafter referred to as MEK) is known to be involved in the regulation of cell proliferation as a kinase that mediates Raf-MEK-ERK signal transduction pathway, and the Raf family (B-Raf, C-Raf etc.) activates the MEK family (MEK-1, MEK-2 etc.) and the MEK family activates the ERK family (ERK-1 and ERK-2).
Activation of Raf-MEK-ERK signal transduction pathway in cancer, particularly colorectal cancer, pancreatic cancer, lung cancer, breast cancer and the like, has been frequently observed.
In addition, since the signals produced by signal molecules such as growth factor, cytokine and the like converge to the activation of MEK-ERK, inhibitors of these functions are considered to more effectively suppress Raf-MEK-ERK signal transduction than suppression of the function of upstream kinases such as RTK, Ras, and Raf.
Moreover, it is also known that a compound having MEK inhibitory activity effectively induces inhibition of ERK1/2 activity and suppression of cell proliferation (The Journal of Biological Chemistry, vol. 276, No. 4, pp. 2686-2692, 2001), and the compound is expected to show effects on diseases caused by undesirable cell proliferation, such as tumor genesis and/or cancer.
It would be useful to provide a novel therapy which provides more effective and/or enhanced treatment of an individual suffering the effects of cancer.